Belt tensioners are well known in the prior art and have been used in many belt systems heretofore. A belt tensioner is a movable support structure that rotatably supports a portion of a belt in an engine or other mechanical system. A belt tensioner is movable to compensate for increases or decreases in belt path length due to belt wear, engine temperature, and other factors to provide a constant belt tensioning force on a timing or drive belt.
In a serpentine belt system, the belt to be tensioned by the belt tensioner is typically trained about a driving crankshaft pulley forming part of the belt system and a sequence of driven pulleys. The driven pulleys are connected to shafts which operate various engine components and/or vehicle accessories.
In order to route the belt around the sequence of driven pulleys and provide sufficient belt wrap around the associated pulleys, the use of idler pulleys are often desirable. However, there is always a need in the automotive art to conserve the space at the front portion of the engine, and to reduce the number of components and weight of the vehicle.
It has been proposed in the expired art to provide the benefits of an idler pulley while conserving engine space and reducing parts by providing the idler pulley as part of a belt tensioning assembly. Specifically, see U.S. Pat. No. 1,675,671. However, this patent discloses an arrangement in which an arm 12, having a pulley 14 mounted thereon, is rotatable about a fixed post 5 and an idler pulley 16 is mounted on a rotatable sleeve 9. The arrangement lacks a fixed pivot structure.
The '671 patent is not only lacking a fixed pivot structure as described above, but also discloses the use of a flat coil spring, as opposed to a more desirable helical coil spring. While the helical type coil spring is preferred for belt tensioners, they apply an axial force that must be contained. The manner in which to contain the axial spring force and simultaneously mount an idler pulley in an efficient manner is another aspect that is dealt with in accordance with the present invention.